title: Contribution of gene-specific lesions, DNA-replication-associated damage, and subsequent transcriptional inhibition in topoisomerase inhibitor-mediated apoptosis in lymphoma cells.
abstract: Lymphoid lineage tumor cells differ widely in their relative sensitivity or resistance to the induction of apoptosis by a variety of chemotherapeutic drugs. We used a model system of virally transformed B- and T-lymphoma cell lines to show that avian T-lymphoma cells are highly resistant, whereas B-lymphoma cells are highly sensitive, to the induction of apoptosis by a wide spectrum of chemotherapeutic drugs that induce different types of lesions in DNA. Among the various drugs examined, the topoisomerase inhibitors, camptothecin, actinomycin D, and etoposide, were the most potent inducers of apoptosis. Examination of the relative contribution of DNA replication and transcriptional inhibition to the differential induction of apoptosis by the topoisomerase inhibitors revealed that the signals initiating the apoptotic response vary, even among compounds with similar cellular targets. Specifically, DNA replication plays a major role in the induction of camptothecin-induced apoptosis, and a lesser role in the induction of apoptosis by etoposide. In contrast, DNA replication is not involved in the induction of apoptosis by actinomycin D. Transcriptional inhibition may provide the major cellular signal for apoptosis induction by this compound. In addition, we determined that the extent of topoisomerase I-cleavable complex inhibition is similar even in genes that are transcribed at different levels and by different RNA polymerases. An overexpressed c-myc gene is no more vulnerable to topoisomerase inhibition than its normally expressed counterpart. In contrast, even under conditions yielding similar amounts of topoisomerase inhibition, rRNA genes are more sensitive to transcriptional inhibition than are the c-myc genes.
authors.affiliation: Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA.
authors.forename: D E
authors.initials: DE
authors.lastname: Muscarella
authors.forename: M K
authors.initials: MK
authors.lastname: Rachlinski
authors.forename: J
authors.initials: J
authors.lastname: Sotiriadis
authors.forename: S E
authors.initials: SE
authors.lastname: Bloom
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002166:Camptothecin / Q000633:toxicity*; D002472:Cell Transformation, Viral; D002645:Chickens; D004249:DNA Damage; D004261:DNA Replication; D004275:DNA, Ribosomal / Q000235:genetics / Q000378:metabolism; D003609:Dactinomycin / Q000633:toxicity*; D005047:Etoposide / Q000633:toxicity; D016259:Genes, myc; D007700:Kinetics; D016393:Lymphoma, B-Cell; D016399:Lymphoma, T-Cell; D059004:Topoisomerase I Inhibitors; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D004275:DNA, Ribosomal; D059004:Topoisomerase I Inhibitors; D003609:Dactinomycin; D005047:Etoposide; D002166:Camptothecin